Regulations passed by the Federal Communications Commission (FCC) in the mid 1980s require each handset in the United States to have a unique identifier. Currently, mobile phones are identified by a 32-bit number called the Electronic Serial Number (ESN). Due to rapid growth in wireless communications, the ESN space is being rapidly exhausted. By some estimates, the ESN space will be completely exhausted by 2007.
Recognizing the prospect of ESN exhaustion, the CDMA industry has defined a new identifier called the Mobile Equipment Identifier (MEID), which is introduced in Release D of the cdma2000 standards (IS-2000-D). However, systems implementing Release D are not expected to be deployed in the near future. Due to the anticipated exhaustion of ESNs, there is great interest in transitioning to the MEID before TIA-2000-D systems are deployed.
In 2005, the Third Generation Partnership Project 2 (3GPP2) introduced a new air interface standard to accommodate the introduction of mobile stations equipped with MEIDs. The standard is published as 3GPP2 C.S0072, also known as TIA-1082, which is incorporated herein by reference. This standard allows deployed releases (Releases 0, A, B, C) of the cdma200 standard to use a limited set of features in Release D to support the MEID. The MEID is used by the circuit-switched core network to identify the mobile station and may also be used by the packet-switched core network for accounting purposes. The mobile station generates a pseudo ESN (pESN) based on its MEID for use in access messages. The pESN has the same format as a ESN. If the network has implemented TIA-1082 and supports the MEID, the network may query the mobile station to determine its MEID. Because different MEIDs may yield the same pESN, the circuit-switched core network may use the pESN and International Mobile Station Identifier (IMSI) to identify the mobile station, or query the mobile station for its MEID. The packet-switched network may use the pESN and IMSI to identify the mobile station for accounting purposes. The MEID may be stored by the circuit-switched core network and sent to the base station.
In conventional networks, ESNs are normally used to derive public long code masks (PLCMs). In systems that support the MEID, the PLCM may be derived from the MEID or pESN. If the pESN is used to derive the PLCM, there is a possibility that multiple mobile stations will have the same pESN. To avoid problems caused by duplicate pESNs, the new standard also allows the base stations to assign PLCMs to mobile stations. The PLCM may be sent to the mobile station in either an Enhanced Channel assignment Message (ECAM) or Universal Handoff Direction Message (UHDM). The new standard also provides a means for the network to query the mobile station to determine its MEID.
Both the base station and the Mobile Switching Center (MSC) in cdma2000 networks may initiate a status inquiry to the mobile station to retrieve the MEID. A method is needed to allow the MSC and BS to share this information to avoid implementations where each node (e.g., base station or MSC) relies on the other to initiate a status inquiry and the MEID not being retrieved, or where each node autonomously initiates the status inquiry resulting in unnecessary signaling over the air. Since the MEID may be useful both to the base station (to forward toward the Packet Data Serving Node (PDSN) for accounting purposes) and to the MSC (for purposes of identification of the mobile station), the MEID retrieved by one node should be communicated to the other node.